1. Field of the Invention
This patent applies to proton exchange membrane electrolyte fuel cells and electrochemical compressors. In particular it applies to polymeric proton exchange membrane (PEM) fuel cells and electrochemical compressors.
2. Description of Prior Art
Present construction of polymer exchange membrane (PEM) fuel cells has evolved from such designs as those of Grubb, Niedrach, and Adlhart, among others. All of these designs employ reactant gas seals which have at least one sealing surface which directly contacts the membrane electrolyte. This requires that the ion exchange membrane itself be extended outside of the active catalytic area of the cell. These designs require the membrane to bridge gaps in cell components such as reactant gas flow fields. Such designs typically result in exposure of the membrane edge to ambient air and/or cooling liquid as well. Since most ion exchange membranes are not very strong, bridging of gaps in cell components can result in high mechanical stresses in and eventually failure of the membrane. Such construction often requires either the use of strong, solid, flow field materials such as graphite, or limitation of the cell to low differential pressures. Exposure of the membrane to ambient air can result in drying of the membrane and exposure to cooling liquid creates the possibility for metal ion contamination. Both of these effects reduce the performance of the fuel cell. In present designs, the membrane can be subjected to substantial mechanical loads created both during and after stack assembly. These loads arise from the compression of seals and/or gaskets and creep of components after assembly. Another disadvantage of present cells is that they are inherently difficult to handle and store since the membrane is unprotected. A very important feature of this invention is that it minimizes the use of the most expensive elements of the conventional PEM fuel cell, which are the carbon paper components such as the electrode, and the membrane.
Accordingly, it is an object of the present invention to provide an inexpensive structure which minimizes the use of expensive components such as the membrane electrolyte and the electrodes.
Another object of the present invention is to provide for ease and low cost of manufacture by minimizing the number of thermal and pressure bonding steps required in cell construction.
Another object of the present invention is to provide a membrane support structure which minimizes the unsupported exposure of the membrane to high differential pressure.
Yet another object of the present invention is to provide a cell structure which is impervious to gas leakage from the oxidant to fuel or fuel to oxidant side of the cell.
Still another object of the present invention is to eliminate electrical short circuits between anode and cathode electrodes which may occur due to the relative movements of cell parts either during fabrication or during use.
Still another object of the present invention is to provide a structure which minimizes the exposure of the electrolyte membrane to the coolant or to ambient air as well as to provide protection against mechanical damage during handling and storage.